PrepTest 121

[lcid:3582] Prep Test 121 LSAT — Reading Comp — S3 Reading comp

Passage

Questions 20-27  .        The first thing any embryo must do before it can  . develop into an organism is Remaining source text redacted.
Passage walkthrough
Passage Summary

Topic: Science


Paragraph 1

  • Paragraph note
    • Process described; comparisons
  • Views, minor Meta-Structures, and the author's attitude
    • Process - Polarity - First thing embryos do - Determine front/back; top/bottom
    • Comparison - Process of polarity is different across organisms; later development (e.g., limbs, brains) much more similar
    • Examples - Fruit flies, nematodes, humans

Paragraph 2

  • Paragraph note
    • Examples/Contrasts; Question
  • Views, minor Meta-Structures, and the author's attitude
    • Example 1 - Fruit fly - Polarity determined before fertilization, happens quickly after
    • Example 2 - Nematode - Polarity determined by location of fertilization; p-granules form and decide front/back
    • Example 3 - Frogs - Similar to nematodes
    • Example 4 - Humans - Polarity determined much later
    • Question - How is it determined in humans? (“tempting mystery”)

Paragraph 3

  • Paragraph note
    • Similarities after polarity determined; Paradox
  • Views, minor Meta-Structures, and the author's attitude
    • Post-polarity genes are similar across species
    • Example - Eye genes are similar in flies, mice, humans
    • Paradox - When most similar (embryo), use different mechanisms; when most different (identifiable species), use the same mechanisms

Main Point: While later development of organisms across species relies on similar genes for similar functions/body parts, early embryonic development of polarity shows a variety of different mechanisms across those same species.

Key Lines?

Lines 1-4 - Process defined

Lines 4-8 - Process compared between species and to other processes

Lines 42-44 - Question/mystery raised

Lines 45-47 - Lines 45-46 - Shift to discussing similarities

Lines 51 - 57 - A paradox

Meta-Structure?

Phenomenon/Explanation - As with many (if not most) Science passages, this one features a phenomenon - the determination of polarity (Lines 1-4) - that needs an explanation. In this case, the Author offers explanations for how polarity is determined - but these processes are very different between organisms (Lines 4-7), which leads us to our next two Meta-Structures...

Comparisons - The passage includes two sets of comparisons that are directly connected, and they’re summed up in Lines 4-8. The Author says that the mechanisms to determine polarity are far more different between organisms than are the processes for later development. So, in other words, organisms have different processes for determining polarity, and similar processes for later development. Which leads us to...

Generalization/Examples - That comparative statement is a Generalization, and the Author then dives into many examples of the different processes of determining polarity (Paragraph 2), and an example of the similar later processes in Lines 49-51. This generalization and these examples all build to...

Paradox/Resolution - The Author explicitly references a paradox, starting in Line 51. That paradox? When species are most similar (embryos, just a few cells), the processes they use to develop are the most different; when they’re most different (developed enough to tell the different species), the processes they use to develop are the most similar. The Author doesn’t present an explanation or resolution for why this might be so, so the Paradox itself is the point of this discussion!

Meta-Structure Wrap-Up - All of these Meta-Structures are substantial in the passage and relate to each other, so they’re all related to the main point. Phenomenon/Explanation passages tend to have the Author’s explanation serve as the main point. Comparison passages tend to have that type of language featured in the main point. Generalization/Examples passages tend to have the generalization as the main point, and Paradox/Resolution passages tend to have the resolution, when one is offered, as the main point - otherwise, the paradox itself is the main point. All of these Meta-Structures deal with the same central topic - the similarities and differences between processes of various species at different stages of development, and particularly the differences in how polarity is determined. Bringing all of this together leads us to the main point, as we summarized it above (and also see the Last Thoughts? note).

Question/Answer - The Author ends Paragraph 2 with a “tempting mystery,” suggesting a question that researchers will be interested in investigating - how polarity is established in mammals. No answer is presented, and no research is offered to indicate a potential answer. Since this is a small line that doesn’t support a broader view or have an answer provided, it’s likely to show up in only a single question.

Last Thoughts?

Note how we phrased the main point - it reflects the paradox and comparisons, but it puts the information about the similarities later first, and the differences earlier last. That’s because the focus on the passage is on that earlier process of determining polarity - it kicks off the passage, and it serves as the focus of that very long Paragraph 2.

Also, this passage is notoriously difficult, but note that it’s very much based on the comparative generalization - the entire Paragraph 2 is meant just to back up a part of that generalization! While the examples themselves can be tricky, and there’s a lot of science involved (what’s a p-granule?!!?!), we don’t really need to know that science - just that the passage is presenting different ways that polarity is determined in different species. Let’s keep this big-picture in mind as we approach the questions.

Question prompt

The passage provides information Remaining source text redacted.
Why the credited answer is right

Credited answer: D

The notes below walk through why it fits the stem and how to eliminate the rest.

Question Type

Science

Strategy Overview

Review the comparisons from the passage relating humans and fruit flies, then find an answer that reflects it

Answer Anticipation

This can be a time-consuming question if you try to find all the information on fruit flies and humans. After all, the fruit fly example takes up a lot of Paragraph 2, and humans show up as examples in a few parts of the passage.However, the entire passage was based around a general comparison - species have very different processes for determining polarity early in their development, and very similar processes for determining polarity later in their development. Instead of trying to digest all the details on fruit flies and humans while trying to infer any comparisons, let’s use this overall comparison as an initial lens for each answer before using the passage to check details on the answers that line up with it.

Answer choices

  1. A
    Since humans and fruit Remaining source text redacted.
    Why choice A is not credited

    (A) Behavior? Nothing in the passage discusses or implies anything about behavior, so this answer is out of scope.

  2. B
    For the elaboration of Remaining source text redacted.
    Why choice B is not credited

    (B) This answer doesn’t line up with the generalization in the passage, where the Author argues that later development is similar between species, not different, as this answer choice states.

  3. C
    Positional information for establishing Remaining source text redacted.
    Why choice C is not credited

    (C) This answer also doesn’t line up with the generalization in the passage, in that it talks about similarities between fruit flies and humans in determining polarity, whereas the passage was about differences in that process. While the passage does say that there are some species that have similar processes (nematodes and frogs, for instance), fruit flies and humans weren’t on that list. And, in fact, the passage says that the process for mammals - including humans - is still a mystery!

  4. D
    A study of the Remaining source text redacted.
    Why choice D matches the stem

    (D) (Lines 49-51) This answer lines up with the generalization that we identified as serving as the main point of the passage. There, the Author argues that processes are dissimilar during the determination of polarity early on, and similar later on. As such, studying those later processes in fruit flies would be more likely to provide information relevant to humans than studying the earlier processes. Additionally, this specific example is cited in Paragraph 3, further reinforcing it as the correct answer.

  5. E
    While the fruit fly Remaining source text redacted.
    Why choice E is not credited

    (E) This answer brings up differences between humans and fruit flies, which doesn’t fully line up with the generalization that serves as the central thesis of this passage. That generalization brought up both similarities and differences between organisms. Additionally, this answer states that a nervous system is a requirement for limb development in humans, and we would have noted such a statement while reading.

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